摘要：when you new a objectit will call the class constructorif the class is subclass of baseclassit will firstly call the baseclass constructorproblem:the baseclass has no 0 arguments constructorwhensubclass s=new subclass()(subclass extend baseclass)will expose an erroryou must special arguments to the 阅读全文

摘要：detegate like a kind of method which has the same arguments and returnswhen you call a detegate you call all the method in related with it but return the last method returns 阅读全文